I've noticed that very smart people often go to great effort to spend time with other very smart people; and then, instead of listening to them, try to talk as much as they can. Which defeats much of the purpose of spending time with very smart people.

I think this is an interesting observation, but I find myself wondering if it really does defeat the purpose. When conversing with someone I suspect is smarter than me, I tend to value direct, critical responses to my own statements and speculations more than whatever smart thing happens to be on their mind. It's far easier (for me) to learn from having been wrong than it is just from hearing something that turns out to be right. I can't elicit as many of those responses if all I do is listen.